Thermoelectric switch



June 23, 1953 JJA. RODDEN 2,643,312

THERMOELECTRI'C SWITCH Filed June 11, 1951 John A. Rodden INVENTOR. 1

Patented June 23, 1953 UNITED STATES PATENT OFFICE THERMOELECTRIC SWITCH John A. Rodden, Pontiac, Mich.

Application June 11, 1951, Serial No. 230,860

4 Claims.

This invention relates to new and useful improvements in thermal responsive electric switches, and pertains more particularly to a switch of this type especially well suited for use in fire warning circuits.

The primary object of this invention is to provide an adjustable thermal responsive switch of such a character that any number of the same may be readily and securely bridged in parallel across a pair of conduits in a fire warning system.

Another important object of this invention is to provide a switch of this character which will be of simple, economical and durable construction, and which will be thoroughly dependable in operation.

A. meritorious feature of the present invention resides in the construction of the base block whereby a single fastener may be utilized to secure a contact strip, an electrical conducting member and its insulation together Still another important feature of the present invention resides in the means provided for adjustably spacing the contact strips, and the incorporation of such means with a means for securing the adjustable contact strip to the base block.

A final important feature of the present invention to be specifically enumerated herein resides in the provision of clamps at the opposite ends of the base block for securing electrical conduits to the electrically conducting elements of the base block.

These, together with various ancillary objects and features of the invention, which will become apparent as the following description proceeds, are attained by the present invention, a preferred embodiment of which has been illustrated by way of example only, in the accompanying drawings, wherein:

Figure 1 is a perspective view of the electric switch showing the same installed for use, and the protective cover of the same raised;

Figure 2 is a longitudinal vertical sectional view taken through the electric switch, and

Figure 3 is a perspective view of the spring disk utilized in the adjusting means for the switch.

Reference is now made more specifically to the accompanying drawings, wherein like numerals designate similar parts throughout the various views, and in which the numeral l9 designates the switch generally.

The switch I comprises a composite base block formed of an inverted T-shaped insulating mem- 2 her l2, and a pair of electrically conductive L-shaped elements It and 16, the latter elements being arranged to overlap the oppositely extending portions of the T-shaped member [2 as clearly shown in Figure 1.

A pair of clamping plates I8 and 20 are disposed at the opposite extremities of the elements I4 and I6, each of the plates l8 and 26 being detachably secured to the elements by means of vertically spaced screw fasteners 22. The faces of the clamping plates [8 and 20 adjacent the elements [4 and I 6, respectively, are provided with conduit receiving grooves 24.

A contact strip 26 is secured in the element l6, and the element It is secured to the insulating member I2 bymeans of a threaded bolt 28 extending through the overlapping portions of the member I2 and the element I6, as well as through the contact strip 26, such bolt 28 being provided with a nut 30.

The element I4 is secured to the insulating member l2 by means of a bushing 32 extending into aligned openings in the element M and the member 12, such bushing 32 being provided with an internally threaded bore which receives the threaded shank 34 of a screw fastener 36. The bushing 32 as well as the screw fasteners 35 are provided with enlarged heads having kerfs therein, as clearly shown in the drawings, whereby the screw fastener 35 may be turned relative to the bushing 32 to adjust the spacing of the heads of the bushings 32 and the screw fastener. A second contact strip 38 is provided through which the screw fastener 36 extends, the head of the screw fastener 35 bearing against the contact strip 38, and a disk spring 40, more clearly shown in Figure 3, embraces the threaded shank 3d and is disposed between the contact strip 38 and the upper surface of the element 14. As will be appreciated, the arrangement is such that the vertical position of the contact strip 33 may be adjusted by turning of the screw fastener 38. The purpose of this arrangement will presently appear.

The adjacent ends of the contact strips 26 and 38 overlap each other with the contact strips being so bent that the overlapping portions of the contact strips are spaced above the insulating member l2. In addition, the adjacent sides of the overlapping portions of the contact strips 26 and 38 are provided with suitable electrical contacts 42 and 44, preferably bronze. Either one of both of the contact strips 26 and 38 is of bimatallic construction, so that the contacts 42 and 44 will move toward and away from each other upon temperature changes. It will be understood that while only the contact strip 26 is shown of being of bimetallic construction, that alternatively the contact strip 38 may be of bimetallic construction or that both of such strips may be of bimetallic construction. As thus far described, it will be evident that upon the strips 26 and 33 attaining a predetermined temperature, the contacts 42 and 44 will cometogether, and that such predetermined temperaturemay be adjusted by use of the screw 36.

In use, the plates I 8 and 2B are sufliciently loosened, or entirely removed by use of the screws 22 so that electrical conduits 58 and it-array be placed in the grooves 24 therein, after which 2. In a thermal responsive switch, a base member including an inverted T-shaped insulating member, a pair of inverted L-shaped conducting blocks interfitting with said T-shaped block, a pair of contact strips carried by said conductive blocks, said strips having ends arranged in overlapping normally spaced relation, at least one of said strips being of bimetallic thermo flexing construction, so that the end portion thereof moves toward and away from the end portion of "the other strip in response to temperature changes, end blocks secured to said conducting blocks, electrical conductors secured between said end blocks and said conducting the plates [8 and 29 are firmly secured, thereby affording electrical connectionbetween the electrical conduit and the contact strips 25 and 38. It will thus be seen that the electric switch ll! may be positioned to bridge continuous parallel electrical conduits, it bein nly necessary to strip a small quantity of the insulation 5i] from the electrical conduits and t remove the e 1 mi ins plates 18 and 2t.

An insulating cover 52 is provided for the switch [0. The cover 52 includes side walls 5 that are provided with open ended slots Eli for receiving the electrical conduits at and as when the cover 52 is slipped down over the switch it. In addition, one of the side Walls 54 of the cover 52 is provided with an opening 5.8 through which a s rew f s ner, not sh wn, may be xtended and threaded into an internally threaded bore 69 in the member 12 to secure the cover 52,. The over 5 as well as the insulatin m mber it may be of plastic material if desired.

From he ioregoine, t construction and operation of the device will be readily understood and further explanation is believed to be unnecessary. However, since numerous modifications and changes will readily'occur to those sk lled in the art, it is n t desired to um he invention to the exact construction shown and described, and accordingly all suitable modiflcations and equivalents may be resorted to, falling within the scope of the appended claims.

H vin described the invention, what claimed as new is:

.1- In a thermal responsive switch, a composite substantially rectangular block formed of a pair of electrically conductive elements and an intervening insulating member, said insulating memher being of inverted T-shape, said elements being of L-shape with the elements overlapping the insulating member, a pair of contact strips carried by the elements and having overlapping normally vertically spaced end portions, fastening means extending through the overlapping member and elements for securing the same and also securing the contact strips to the blocks, at least one of said strips being of bimetallic con- ,struction so that said end portion thereof moves toward and away from the end portion of the other strip upon temperature changes, and means for securingelectrical conductors to said elements.

blocks, through fasteners securing said conducting blocks and said strip in assembled relation on said insulating member.

3."In a thermal responsive switch, a, base me her including. an inverted T-shaped insulati member, a pair of inverted L-shaped conducti locks interfltting with said T-shaped block, pair of contact strips carried by said conductive blocks, said strips having .ends arranged in overlapping normally spaced relation, at least one of said strips being of bimetallic thermo flexing construction, so that the end portion thereof moves toward and away from the end portion of the other strip in response to temperature changes, end blocks secured to said conducting blocks, electrical conductors secured between said end blocks and said conducting blocks, through fasteners securing said conducting blocks and said strip in assembled relation on said insulating member. one of said through fasteners being a threaded screw engaging a threaded head, a spring washer on said screw and interposed between the respective conducting block and the associated strip.

4. In a thermal responsive switch, .a composite substantially rectangular block including a pair of L-shaped electrically conductive elements and an intervening inverted T-shaped insulating member, said elements overlapping said insulating member, a pair of contact strips carried by the elements and having Overlapping normally vertically spaced free end portions, at least one of the strips being of bimetallic thermo flexing construction so that said end portion thereof moves toward and away from the end portion of the other strip in response to temperature changes, a threaded fastener securing one of the strips and one of the elements to the member, a spring washer interposed between said strip and said element for adjusting said strip vertically with respect to the other strip, electrical conductors secured to the respective elements, a cover for the contact strips detachably secured to the block.

JOHN A. RODDEN.

Country Date France Oct. 31, 1947 Number 

